[PDF] Atoms, Molecules, and Ions

26475_8Chapter2_AtomsMoleculesAndIons.pdf ;]UfjYh .

9jeci( EebYWkbYi( UdX Aedi>_[khY .*-K°ny'αvα âs zâyrpγyrα v° n° r-unyrq oΔrnβu pn° é2Δâπvqr πnyγnoyr v°sâΔznβvâ°1 yrnqv°t βâ rnΔy' qvnt°âα2vα

âs qvαrnαrα âΔ qrβrpβvâ° âs r°πvΔâ°zr°βny r-éâαγΔr 2βâ unΔzsγy αγoαβn°prα3 -pΔrqvβE zâqvsvpnβvâ° âs 2σâΔx o' Znγy

PyâσrΔα.

;]UfjYh Gkjb_dY

736 OnΔy' Sqrnα v° Kβâzvp durâΔ'

737 Oπâyγβvâ° âs Kβâzvp durâΔ'

738 Kβâzvp cβΔγpβγΔr n°q c'zoâyvαz

739 Murzvpny PâΔzγynα

73: dur ZrΔvâqvp dnoyr

73A WâyrpγynΔ n°q Sâ°vp Mâzéâγ°qα

73B Murzvpny Xâzr°pynβγΔr

AdjheXkWj_ed

Zpvs pwfsbmm ifbmui boe tvtdfqujcjmjuz up ejtfbtf efqfoet vqpo uif dpnqmfy joufsbdujpo cfuxffo zpvs hfofujd nblfvq

boe fowjsponfoubm fyqptvsf, xjui uif pvudpnf ejggjdvmu up qsfejdu. Fbsmz efufdujpo pg cjpnbslfst, tvctubodft uibu

joejdbuf bo pshbojtn-t ejtfbtf ps qiztjpmphjdbm tubuf, dpvme bmmpx ejbhoptjt boe usfbunfou cfgpsf b dpoejujpo cfdpnft

tfsjpvt ps jssfwfstjcmf. Sfdfou tuvejft ibwf tipxo uibu zpvs fyibmfe csfbui dbo dpoubjo npmfdvmft uibu nbz cf

cjpnbslfst gps sfdfou fyqptvsf up fowjsponfoubm dpoubnjobout ps gps qbuipmphjdbm dpoejujpot sbohjoh gspn btuinb

up mvoh dbodfs. Tdjfoujtut bsf xpsljoh up efwfmpq cjpnbslfs ≠gjohfsqsjout≤ uibu dpvme cf vtfe up ejbhoptf b tqfdjgjd

ejtfbtf cbtfe po uif bnpvout boe jefoujujft pg dfsubjo npmfdvmft jo b qbujfou-t fyibmfe csfbui. Bo fttfoujbm dpodfqu

voefsmzjoh uijt hpbm jt uibu pg b npmfdvmf-t jefoujuz, xijdi jt efufsnjofe cz uif ovncfst boe uzqft pg bupnt ju

dpoubjot, boe ipx uifz bsf cpoefe uphfuifs. Uijt dibqufs xjmm eftdsjcf tpnf pg uif gvoebnfoubm difnjdbm qsjodjqmft

sfmbufe up uif dpnqptjujpo pg nbuufs, jodmvejoh uiptf dfousbm up uif dpodfqu pg npm-fdvmbs jefoujuz.MunéβrΔ 7 Kβâzα1 Wâyrpγyrα1 n°q Sâ°αAB

.*- =Uhbo AXYUi _d 9jec_W L]Yeho MV γvs sâr ét γvwβ βsqγwéâ1 Véπ -wzz ps opzs2 γéE

•dγoγs γvs øéβγπzoγsβ ét Oozγéâvβ oγé°wq γvséαV

•fβs øéβγπzoγsβ ét Oozγéâvβ oγé°wq γvséαV γé s'øzowâ γvs zo-β ét rstwâwγs 2oâr °πzγwøzs øαéøéαγwéâβ

evs zoâuπous πβsr wâ qvs°wβγαV wβ βssâ oâr vsoαr wâ °oâV rwβqwøzwâsβ1 αoâuwâu tαé° °srwqwâs γé sâuwâssαwâu γé

téαsâβwqβ γé oαγ3 evs zoâuπous ét qvs°wβγαV wâqzπrsβ wγβ é-â σéqopπzoαV oβ -szz oβ wγβ é-â téα° ét βvéαγvoâr3

Nvs°wqoz βV°pézβ oαs πβsr γé αsøαsβsâγ oγé°β oâr szs°sâγβ3 Nvs°wqoz téα°πzoβ rsøwqγ °ézsqπzsβ oβ -szz oβ γvs

qé°øéβwγwéâ ét qé°øéπârβ3 Nvs°wqoz sΔπoγwéâβ øαéσwrs wâtéα°oγwéâ opéπγ γvs ΔπozwγV oâr ΔπoâγwγV ét γvs qvoâusβ

oββéqwoγsr -wγv qvs°wqoz αsoqγwéâβ3

evwβ qvoøγsα -wzz zoV γvs téπâroγwéâ téα éπα βγπrV ét γvs zoâuπous ét qvs°wβγαV3 evs qéâqsøγβ ét γvwβ téπâroγwéâ

wâqzπrs γvs oγé°wq γvséαV1 γvs qé°øéβwγwéâ oâr °oββ ét oâ oγé°1 γvs σoαwopwzwγV ét γvs qé°øéβwγwéâ ét wβéγéøsβ1 wéâ

téα°oγwéâ1 qvs°wqoz péârβ wâ wéâwq oâr qéσozsâγ qé°øéπârβ1 γvs γVøsβ ét qvs°wqoz αsoqγwéâβ1 oâr γvs âo°wâu ét

qé°øéπârβ3 hs -wzz ozβé wâγαérπqs éâs ét γvs °éβγ øé-sαtπz γéézβ téα éαuoâwWwâu qvs°wqoz yâé-zsrusE γvs øsαwérwq

γopzs3

9jec_W L]Yeho j]hek[] j]Y F_dYjYYdj] ;Ydjkho

evs soαzwsβγ αsqéαrsr rwβqπββwéâ ét γvs poβwq βγαπqγπαs ét °oγγsα qé°sβ tαé° oâqwsâγ Rαssy øvwzéβéøvsαβ1 γvs βqwsâγwβγβ

ét γvswα roV3 Tâ γvs twtγv qsâγπαV MN1 Wsπqwøøπβ oâr Os°éqαwγπβ oαuπsr γvoγ ozz °oγγsα -oβ qé°øéβsr ét β°ozz1 twâwγs

øoαγwqzsβ γvoγ γvsV qozzsrPfa]ae1 o γsα° rsαwσsr tαé° γvs Rαssy -éαr téα wwârwσwβwpzs3x evsV γvéπuvγ ét oγé°β oβ

°éσwâu øoαγwqzsβ γvoγ rwttsαsr wâ βvoøs oâr βwWs1 oâr -vwqv qéπzr xéwâ γéusγvsα3 Woγsα1 Lαwβγéγzs oâr éγvsαβ qo°s γé

γvs qéâqzπβwéâ γvoγ °oγγsα qéâβwβγsr ét σoαwéπβ qé°pwâoγwéâβ ét γvs téπα wszs°sâγβxutwαs1 soαγv1 owα1 oâr -oγsαuoâr

qéπzr ps wâtwâwγszV rwσwrsr3 TâγsαsβγwâuzV1 γvsβs øvwzéβéøvsαβ γvéπuvγ opéπγ oγé°β oâr wszs°sâγβx oβ øvwzéβéøvwqoz

qéâqsøγβ1 pπγ oøøoαsâγzV âsσsα qéâβwrsαsr øsαtéα°wâu 2s'øsαw°sâγβ γé γsβγ γvswα wrsoβ3

evs Lαwβγéγszwoâ σws- ét γvs qé°øéβwγwéâ ét °oγγsα vszr β-oV téα éσsα γ-é γvéπβoâr Vsoαβ1 πâγwz Pâuzwβv βqvéézγsoqvsα

Uévâ Oozγéâ vszøsr γé αsσézπγwéâwWs qvs°wβγαV -wγv vwβ vVøéγvsβwβ γvoγ γvs psvoσwéα ét °oγγsα qéπzr ps s'øzowâsr

πβwâu oâ oγé°wq γvséαV3 Qwαβγ øπpzwβvsr wâ 6C5B1 °oâV ét Oozγéâvβ vVøéγvsβsβ opéπγ γvs °wqαéβqéøwq tsoγπαsβ ét °oγγsα

oαs βγwzz σozwr wâ °érsαâ oγé°wq γvséαV3 Ssαs oαs γvs øéβγπzoγsβ ét9Q]gbayf Qgb_YS gXUbel3

1.Xoγγsα wβ qé°øéβsr ét s'qssrwâuzV β°ozz øoαγwqzsβ qozzsr oγé°β3 Lâ oγé° wβ γvs β°ozzsβγ πâwγ ét oâ szs°sâγ

γvoγ qoâ øoαγwqwøoγs wâ o qvs°wqoz qvoâus3

2.Lâ szs°sâγ qéâβwβγβ ét éâzV éâs γVøs ét oγé°1 -vwqv voβ o °oββ γvoγ wβ qvoαoqγsαwβγwq ét γvs szs°sâγ oâr wβ γvs

βo°s téα ozz oγé°β ét γvoγ szs°sâγ -

>_[khY .*..3 L °oqαéβqéøwq βo°øzs ét oâ szs°sâγ qéâγowâβ oâ wâqαsrwpzV

zoαus âπ°psα ét oγé°β1 ozz ét -vwqv voσs wrsâγwqoz2 qvs°wqoz øαéøsαγwsβ3>_[khY .*.A pre-1982 copper penny (left) contains -approximately 3

22copper atoms (several dozen

are represented as brown spheres at the right), -each of which has the same chemical properties. -(credit:

modification of work by "slgckgc"/Flickr)

3.Lγé°β ét éâs szs°sâγ rwttsα wâ øαéøsαγwsβ tαé° oγé°β ét ozz éγvsα szs°sâ2γβ368Chapter 2 Atoms, Molecules, and Ions[qr· lxwÅnwÅ r· iøiruikun ox° o°nn iÅ qÅÅyB331/content/col11760/1.9

4.L qé°øéπâr qéâβwβγβ ét oγé°β ét γ-é éα °éαs szs°sâγβ qé°pwâsr wâ o β°ozz1 -vézs2âπ°psα αoγwé3 Tâ o uwσsâ

qé°øéπâr1 γvs âπ°psαβ ét oγé°β ét soqv ét wγβ 2szs°sâγβ oαs oz-oVβ øαsβsâγ wâ γvs βo°s αoγwé -2>a]liZ .*/.3>a]liZ .*/Bnoodq(HH) nwhcd, _ onvcdqx, ak_bj bnlontmc, qdrtksr eqnl sgd bnlahm_shnm ne- svn sxodr ne

_snlrμbnoodq (aqnvm rogdqdr) _mc nwxfdm (qdc rogdqd-r)μhm _ 1:1 q_shn. (bqdchs: lnchehb_shnm- ne vnqj ax

πBgdlhb_khmsdqdrsσ/Vhjhldch_ Bnllnmr)

5.Lγé°β oαs âswγvsα qαsoγsr âéα rsβγαéVsr rπαwâu o qvs°wqoz qvoâus1 pπγ oαs wâβγsor αsoααoâusr γé Vwszr

βπpβγoâqsβ γvoγ oαs rwttsαsâγ tαé° γvéβs øαsβsâγ pstéαs γvs qvoâus ->a]liZ .*0.3>a]liZ .*0Vgdm sgd dkdldmsr bnoodq (_ rghmx, qdc-aqnvm rnkhc, rgnvm gdqd _r aqnvm rogdqdr)- _mc nwxfdm

(_ bkd_q _mc bnknqkdrr f_r, rgnvm gdqd _r qdc -rogdqdr) qd_bs, sgdhq _snlr qd_qq_mfd sn enql _ -bnlontmc

bnms_hmhmf bnoodq _mc nwxfdm (_ onvcdqx, ak_bj rnkhc). (bqdchs bnoodq: lnchehb_shnm -ne vnqj ax gsso://hl_fdr-

ne-dkdldmsr.bnl/bnoodq.ogo)

Oozγéâvβ oγé°wq γvséαV øαéσwrsβ o °wqαéβqéøwq s'øzoâoγwéâ ét γvs °oâV °oqαéβqéøwq øαéøsαγwsβ ét °oγγsα γvoγ Véπvσs

zsoαâsr opéπγ3 Qéα s'o°øzs1 wt oâ szs°sâγ βπqv oβ qéøøsα qéâβwβγβ ét éâzV éâs ywâr ét oγé°1 γvsâ wγ qoââéγ ps pαéysâ

ré-â wâγé βw°øzsα βπpβγoâqsβ1 γvoγ wβ1 wâγé βπpβγoâqsβ qé°øéβsr ét ts-sα γVøsβ ét oγé°β3 Lâr wt oγé°β oαs âswγvsα

qαsoγsr âéα rsβγαéVsr rπαwâu o qvs°wqoz qvoâus1 γvsâ γvs γéγoz °oββ ét °oγγsα øαsβsâγ -vsâ °oγγsα qvoâusβ tαé° éâs

γVøs γé oâéγvsα -wzz αs°owâ qéâβγoâγ -γvs zo- é2t qéâβsασoγwéâ ét °oγγsα.3

=oVdgcZ .*-Bg_osdq 2 @snlr, Lnkdbtkdr, _mc Hnmr69

LYij_d[

Tâ γvs tézzé-wâu rαo-wâu1 γvs uαssâ βøvsαsβ αsøαsβsâγ oγé°β ét o qsαγowâ szs°sâγ3 evs øπαøzs βøvsαsβ

αsøαsβsâγ oγé°β ét oâéγvsα szs°sâγ3 Tt γvs βøvsαsβ γéπqv1 γvsV oαs øoαγ ét o βwâuzs πâwγ ét o qé°øéπâr3 Oésβ

γvs tézzé-wâu qvs°wqoz qvoâus αsøαsβsâγsr pV γvsβs βV°pézβ σwézoγs oâV ét γvs wrsoβ ét Oozγéâvβ oγé°wq

γvséαVJ Tt βé1 -vwqv éâsJKebkj_ed

evs βγoαγwâu °oγsαwozβ qéâβwβγ ét γ-é uαssâ βøvsαsβ oâr γ-é øπαøzs βøvsαsβ3 evs øαérπqγβ qéâβwβγ ét éâzV

éâs uαssâ βøvsαs oâr éâs øπαøzs βøvsαs3 evwβ σwézoγsβ Oozγéâvβ øéβγπzoγs γvoγ oγé°β oαs âswγvsα qαsoγsr âéα

rsβγαéVsr rπαwâu o qvs°wqoz qvoâus1 pπγ oαs °sαszV αsrwβγαwpπγsr3 -Tâ γvwβ qoβs1 oγé°β oøøsoα γé voσs pssâ

rsβγαéVsr3. ;]YWa Qekh DYUhd_d[

Tâ γvs tézzé-wâu rαo-wâu1 γvs uαssâ βøvsαsβ αsøαsβsâγ oγé°β ét o qsαγowâ szs°sâγ3 evs øπαøzs βøvsαsβ

αsøαsβsâγ oγé°β ét oâéγvsα szs°sâγ3 Tt γvs βøvsαsβ γéπqv1 γvsV oαs øoαγ ét o βwâuzs πâwγ ét o qé°øéπâr3 Oésβ

γvs tézzé-wâu qvs°wqoz qvoâus αsøαsβsâγsr pV γvsβs βV°pézβ σwézoγs oâV ét γvs wrsoβ ét Oozγéâvβ oγé°wq

γvséαVJ Tt βé1 -vwqv éâsJ6afjUe5evs βγoαγwâu °oγsαwozβ qéâβwβγ ét téπα uαssâ βøvsαs2β oâr γ-é øπαøzs βøvsαsβ3 evs øαérπqγβ qéâβwβγ

ét téπα uαssâ βøvsαsβ oâr γ-é øπαøzs βøvsαsβ3 2evwβ résβ âéγ σwézoγs oâV ét Oozγéâvβ øéβγπzoγsβE Lγé°β oαs

âswγvsα qαsoγsr âéα rsβγαéVsr1 pπγ oαs αsrwβγαwpπγsr 2wâ β°ozz1 -vézs2âπ°psα αoγwéβ3

Oozγéâ yâs- ét γvs s'øsαw°sâγβ ét Qαsâqv qvs°wβγ Uéβsøv aαéπβγ1 -vé rs°éâβγαoγsr γvoγP[[ eP]b[Te aU P bgdT

Ra]bag_S Ra_fPX_ fWT eP]T T[T]T_fe X_ fWT eP]T bdabadfXa_ Qk ]Pee

3 evwβ βγoγs°sâγ wβ yâé-â oβ γvs]Qj bV TUVYaYgU

cebcbegYbaféα γvs]Qj bV SbafgQag Sb_cbfYgYba3 evs βπuusβγwéâ γvoγ γvs âπ°psαβ ét oγé°β ét γvs szs°sâγβ wâ o uwσsâ

qé°øéπâr oz-oVβ s'wβγ wâ γvs βo°s αoγwé wβ qéâβwβγsâγ -wγv γvsβs épβsασoγwéâβ3 Qéα s'o°øzs1 -vsâ rwttsαsâγ βo°øzsβ

ét wβééqγoâs -o qé°øéâsâγ ét uoβézwâs oâr éâs ét γvs βγoâroαrβ πβsr wâ γvs éqγoâs αoγwâu βVβγs°. oαs oâozVWsr1 γvsV

oαs téπâr γé voσs o qoαpéâ2γé2vVrαéusâ °oββ αoγwé2 ét :388E61 oβ βvé-â wâLUVbY .*-3

;edijUdj ;ecfei_j_ed eZ AieeWjUdY

KUcfbY ;UhVed @oXhe[YdEUii JUj_e

A 14.82 g 2.78 g

 
H
DBSCPO 
H
IZESPHFO! 
C 
C  
H
DBSCPO 
H
IZESPHFO" 
C 
C  
H
DBSCPO


H
IZESPHFOLUVbY .*-70Chapter 2 Atoms, Molecules, and Ions[qr· lxwÅnwÅ r· iøiruikun ox° o°nn iÅ qÅÅyB331/content/col11760/1.9

It is worth noting that although all samples of a particular compound have the same mass ratio, the converse is not

true in general. That is, samples that have the same mass ratio are not necessarily the same substance. For example,

there are many compounds other than isooctane that -also have a carbon-to-hydrogen mass ratio of 5-.33:1.00.

Dalton also used data from Proust, as well as results from his own experiments, to formulate another interesting law.

Thelaw of multiple proportionsstates thatiWT_ fia T[T]T_fe dTPRf fa Uad] ]adT fWP_ a_T Ra]bag_S% P UXjTS ]Pee

aU a_T T[T]T_f iX[[ dTPRf iXfW ]PeeTe aU fWT afWTd T[T]T_f X_ P dPfXa aU e]P[[% iWa[T _g]QTde. For example, copper

and chlorine can form a green, crystalline solid with a mass ratio of 0.558 g chlorine to 1 g copper, as well as a

brown crystalline solid with a mass ratio of 1.116 g chlorine to 1 g copper. These ratios by themselves may not seem

particularly interesting or informative; however, if we take a ratio of these ratios, we obtain a useful and possibly

surprising result: a small, whole-number ratio. 
H
$M 
H
$V

4EFP 

QL

 O>QFL JB>KP QE>Q QEB ?OLTK @LJMLRKA E>P QTF@B QEB >JLRKQ LC @EILOFKB MBO >JLRKQ LC @LMMBO >P QEB DOBBK@LJMLRKA

4EFP @>K ?B BUMI>FKBA ?V >QLJF@ QEBLOV FC QEB @LMMBO

QL @EILOFKB O>QFL FK QEB ?OLTK @LJMLRKA FP  @LMMBO >QLJ QL 

@EILOFKB >QLJP >KA QEB O>QFL FK QEB DOBBK @LJMLRKA FP  @LMMBO >QLJ QL  @EILOFKB >QLJ 4EB O>QFL LC @EILOFKB >QLJP

>KA
QERP
QEB
O>QFL
LC
QEBFO
J>PPBP
FP
QEBOBCLOB

QL

>a]liZ .*1).>a]liZ .*1Compared to the copper chlorine compound in (a),- where copper is represented by brown spheres an-d

chlorine by green spheres, the copper chlorine com-pound in (b) has twice as many chlorine atoms -per copper atom.

(credit a: modification of work by "Benjah-bmm2-7"/Wikimedia Commons; credit b: modification -of work by

"Walkerma"/Wikimedia Commons) =oVdgcZ .*.

EVnj f[

A sample of compound A (a clear, colorless gas) is analyzed and found to contain 4.27 g carbon and 5.69

g oxygen. A sample of compound B (also a clear, colorless gas) is analyzed and found to contain 5.19 g

carbon and 13.84 g oxygen. Are these data an example of the law of definite proportions, the law of multiple

proportions, or neither? What do these data tel-l you about substances A and B?

Lfclkafe

In compound A, the mass ratio of carbon to -oxygen is:Chapter 2 Atoms, Molecules, and Ions71 In compound B, the mass ratio of carbon to -oxygen is:

4EB
O>QFL
LC
QEBPB
O>QFLP
FP


H
0 
H
$

4EFP PRMMLOQP QEB I>T LC JRIQFMIB MOLMLOQFLKP 4EFP JB>KP QE>Q ! >KA " >OB AFCCBOBKQ @LJMLRKAP TFQE !

E>SFKD LKB

E>IC >P JR@E @>O?LK MBO >JLRKQ LC LUVDBK LO QTF@B >P JR@E LUVDBK MBO >JLRKQ LC @>O?LK >P "
!
MLPPF?IB
M>FO
LC
@LJMLRKAP
QE>Q
TLRIA
CFQ
QEFP
OBI>QFLKPEFM
TLRIA
?B
!

#/

2and B = CO.

Fmjho bsyv Ojfvrnrl

A sample of compound X (a clear, colorless, combustible liquid with a noticeable odor) is analyzed and

found to contain 14.13 g carbon and 2.96 g hydrogen. A sample of compound Y (a clear, colorless,

combustible liquid with a noticeable odor that is slightly different from X's odor) is analyzed and found to

contain 19.91 g carbon and 3.34 g hydrogen. Are these data an example of the law of definite proportions,

the law of multiple proportions, or neither? Wh-at do these data tell you about substances X -and Y?

6afjUe5In compound X, the mass ratio of carbon to -hydrogen is

)K
@LJMLRKA
9
QEB
J>PP

O>QFL
LC
@>O?LK
QL
LUVDBK
FP

4EB
O>QFL
LC
QEBPB
O>QFLP
FP 
H
$ 
H
)    4EFP
PJ>II
TELIB

KRJ?BO
O>QFL
PRMMLOQP
QEB
I>T
LC
JRIQFMIB

MOLMLOQFLKP
4EFP
JB>KP
QE>Q
8
>KA
9
>OB
AFCCBOBKQ
@LJMLRKAP

3/3 Hzspyxnsr sk Dxsqnh Wmjsvé

By the end of this section, you will be able- to:

•Outline milestones in the development of modern ato-mic theory •Summarize and interpret the results of the experime-nts of Thomson, Millikan, and Rutherford •Describe the three subatomic particles that compose -atoms •Define isotopes and give examples for several eleme-nts

In the two centuries since Dalton developed his ideas, scientists have made significant progress in furthering our

understanding of atomic theory. Much of this came from the results of several seminal experiments that revealed the

details of the internal structure of atoms. Here, we will discuss some of those key developments, with an emphasis

on application of the scientific method, as well as understanding how the experimental evidence was analyzed. While

the historical persons and dates behind these experiments can be quite interesting, it is most important to understand

the concepts resulting from their work.72Chapter 2 Atoms, Molecules, and Ions[qr· lxwÅnwÅ r· iøiruikun ox° o°nn iÅ qÅÅyB331/content/col11760/1.9

9jec_W L]Yeho UZjYh j]Y F_dYjYYdj] ;Ydjkho

Tt °oγγsα -sαs qé°øéβsr ét oγé°β1 -voγ -sαs oγé°β qé°øéβsr étJ hsαs γvsV γvs β°ozzsβγ øoαγwqzsβ1 éα -oβ γvsαs

βé°sγvwâu β°ozzsαJ Tâ γvs zoγs 6C55β1 o âπ°psα ét βqwsâγwβγβ wâγsαsβγsr wâ Δπsβγwéâβ zwys γvsβs wâσsβγwuoγsr γvs

szsqγαwqoz rwβqvoαusβ γvoγ qéπzr ps øαérπqsr wâ zé-2øαsββπαs uoβsβ1 -wγv γvs °éβγ βwuâwtwqoâγ rwβqéσsαV °ors pV

Pâuzwβv øvVβwqwβγ U3 U3 evé°βéâ πβwâu o qoγvérs αoV γπps3 evwβ oøøoαoγπβ qéâβwβγsr ét o βsozsr uzoββ γπps tαé° -vwqv

oz°éβγ ozz γvs owα vor pssâ αs°éσsrF γvs γπps qéâγowâsr γ-é °sγoz szsqγαérsβ3 hvsâ vwuv σézγous -oβ oøøzwsr oqαéββ

γvs szsqγαérsβ1 o σwβwpzs pso° qozzsr o qoγvérs αoV oøøsoαsr psγ-ssâ γvs°3 evwβ pso° -oβ rstzsqγsr γé-oαr γvs

øéβwγwσs qvoαus oâr o-oV tαé° γvs âsuoγwσs qvoαus1 oâr -oβ øαérπqsr wâ γvs βo°s -oV -wγv wrsâγwqoz øαéøsαγwsβ

-vsâ rwttsαsâγ °sγozβ -sαs πβsr téα γvs szsqγαérsβ3 Tâ βw°wzoα s'øsαw°sâγβ1 γvs αoV -oβ βw°πzγoâséπβzV rstzsqγsr

pV oâ oøøzwsr °ouâsγwq twszr1 oâr °soβπαs°sâγβ ét γvs s'γsâγ ét rstzsqγwéâ oâr γvs °ouâsγwq twszr βγαsâuγv ozzé-sr

evé°βéâ γé qozqπzoγs γvs qvoαus2γé2°oββ αoγwé ét γvs qoγvérs αoV øoαγwqzsβ3 evs αsβπzγβ ét γvsβs °soβπαs°sâγβ

wârwqoγsr γvoγ γvsβs øoαγwqzsβ -sαs °πqv zwuvγsα γv2oâ oγé°β ->_[khY .*2.3>_[khY .*2(a) J. J. Thomson produced a visible beam- in a cathode ray tube. (b) This is an -early cathode ray tube,

invented in 1897 by Ferdinand Braun. (-c) In the cathode ray, the beam (shown in yellow) comes from the -cathode and

is accelerated past the anode toward a fluorescent -scale at the end of the tube. Simultaneous de-flections by applied

electric and magnetic fields permitted Thomson to c-alculate the mass-to-charge ratio of the particles -composing the

cathode ray. (credit a: modification of work by Nobel -Foundation; credit b: modification of work by -Eugen Nesper;

credit c: modification of work by "Kurzon"/Wikim-edia Commons)

Moβsr éâ vwβ épβsασoγwéâβ1 vsαs wβ -voγ evé°βéâ øαéøéβsr oâr -vVE evs øoαγwqzsβ oαs oγγαoqγsr pV øéβwγwσs -0.

qvoαusβ oâr αsøszzsr pV âsuoγwσs -}. qvoαusβ1 βé γvsV °πβγ ps âsuoγwσszV qvoαusr -zwys qvoαusβ αsøsz oâr πâzwys

qvoαusβ oγγαoqγ.F γvsV oαs zsββ °oββwσs γvoâ oγé°β oâr wârwβγwâuπwβvopzs1 αsuoαrzsββ ét γvs βéπαqs °oγsαwoz1 βé γvsV

°πβγ ps tπâro°sâγoz1 βπpoγé°wq qéâβγwγπsâγβ ét ozz oγé°β3 Lzγvéπuv qéâγαéσsαβwoz oγ γvs γw°s1 evé°βéâvβ wrso -oβ

uαorπozzV oqqsøγsr1 oâr vwβ qoγvérs αoV øoαγwqzs wβ -voγ -s âé- qozz oâU]USgeba1 o âsuoγwσszV qvoαusr1 βπpoγé°wqChapter 2 Atoms, Molecules, and Ions73

particle with a mass more than one thousand-times less that of an atom. The term "electron" was coined in 1891 by

Irish physicist George Stoney, from "dkdbsqic inm." Click_ZiZ %_kkg6++fgZejkVoXfccZ]Z*fi]+c+-2CCM_fdjfe-&to hear Thomson describe his discovery in his own voice.

In 1909, more information about the electron was uncovered by American physicist Robert A. Millikan via his "oil

drop" experiments. Millikan created microscopic oil droplets, which could be electrically charged by friction as they

formed or by using X-rays. These droplets initially fell due to gravity, but their downward progress could be slowed

or even reversed by an electric field lower in the apparatus. By adjusting the electric field strength and making careful

measurements and appropriate calculations, Millikan was able to determine the charge on individual drops (

>a]liZ

.*3).>a]liZ .*3Millikan's experiment measured the charge of individual oil -drops. The tabulated data are examples of a

few possible values.

Looking at the charge data that Millikan gathered, you may have recognized that the charge of an oil droplet is always

a multiple of a specific charge, 1.6 -19C. Millikan concluded that this value must therefore be a fundamental

charge - the charge of a single electron - with his measured charges due to an excess of one electron (1 times 1.6

 -19C), two electrons (2 times 1.6 -19C), three electrons (3 times 1.6 -19C), and so on, on a given oil

droplet. Since the charge of an electron was now known due to Millikan's research, and the charge-to-mass ratio wasEaeb kf EZVieae]

74Chapter 2 Atoms, Molecules, and Ions[qr· lxwÅnwÅ r· iøiruikun ox° o°nn iÅ qÅÅyB331/content/col11760/1.9

already known due to Thomson's research (1.759

11C/kg), it only required a simple calculation to determine

the mass of the electron as well. Ч  

Politique de confidentialité -Privacy policy